Conjoined gas turbine interface seal

ABSTRACT

A device including a conjoined laminate interface seal shaped for reducing inter-seal gap (e.g., an angled gap, an ‘L’-shaped gap, etc.) leakage in gas turbines is disclosed. In one embodiment, a seal device for a gas turbine includes: a first flange shaped to be disposed within a first slot of a first arcuate component and a first adjacent slot of a second arcuate component; a conjoined layer connected to a first surface of the first flange, the first surface configured to face a working fluid flow of the gas turbine; and a second flange shaped to be disposed within a second slot of the first arcuate component and a second adjacent slot of the second arcuate component, the second flange including a second surface connected to the conjoined layer.

FIELD OF THE INVENTION

This invention relates generally to power plant systems and, more particularly, to conjoined seal systems (e.g., a conjoined laminate seal system) and devices for reducing interface leakage losses in gas turbines.

BACKGROUND OF THE INVENTION

The operation of some power plant systems, for example certain simple-cycle and combined-cycle power plant systems, include the use of gas turbines. The operation of these gas turbines includes the use of pressurized fluid flows at extreme temperatures traveling through flowpaths of the gas turbine, these pressurized fluid flows regulating operation of the turbine and driving a rotor of the turbine (e.g., power generation). The working fluid flow path (e.g., the main gas-flow path) in a gas turbine commonly includes the operational components of a compressor inlet, a compressor, a turbine section and a gas outflow. There are also secondary flows that are used to cool the various heated components of the turbine, these secondary flows passing about an outside surface of the turbine components and remaining substantially isolated from the main gas-flow path. Mixing of these flows and gas leakage in general, from or into the gas-flow path, may be detrimental to turbine performance.

The operational components of a gas turbine are contained in a casing. The turbine is commonly surrounded annularly by adjacent arcuate components. As used herein, the term “arcuate” may refer to a member, component, part, etc. having a curved or partially curved shape. The adjacent arcuate components include outer shrouds, inner shrouds, nozzle blocks, and diaphragms. Arcuate components may provide a container for the gas-flow path in addition to the casing alone. Arcuate components may secure other components of the turbine and define spaces within the turbine. Between each adjacent pair of arcuate components is an interface (e.g., a space, a gap, etc.) that permits thermal expansion of the arcuate components of the gas turbine. During operation, working fluid (e.g., a high temperature flow) may flow through an interior of the container formed by an inside surface of the arcuate components, and cooling flows may pass across an outer surface of the arcuate components.

Slots are defined on the sides of each arcuate component for receiving a set of seals in cooperation with an adjacent slot of an adjacent arcuate component. The set of seals are placed in the slot to prevent leakage across the interface (e.g., between the areas of the turbine on either side of the seal). These areas include the main gas-flow path and secondary cooling flows which pass across the outer surface of the turbine components (e.g., arcuate components) to thermally regulate the gas turbine. These secondary cooling flows substantially surround the main gas-flow path at a high pressure relative to a pressure of the main gas-flow path.

The slots within the end of a particular arcuate component may be connected and be angled in orientation relative to one another. As a result, when a set of planar seals is inserted in to the slots of a given arcuate component, a gap is formed between the set of planar seals. This gap permits leakage between the internal and external areas of the gas turbine (e.g., between secondary cooling flows and the main gas-flow path). Reducing this gap improves gas turbine performance. In some systems, a third seal may be connected on a top surface of adjacent planar seals to span the gap there between and partially obstruct leakage flow through the gap. However, this third seal may cover the gap from the high pressure side but not seal the gap between the set of planar seals. During operation fluid may still flow along the length of the set of planar seals on the low pressure side beneath the third seal.

BRIEF DESCRIPTION OF THE INVENTION

A first aspect of the disclosure provides a seal device for a gas turbine including: a first flange shaped to be disposed within a first slot of a first arcuate component and a first adjacent slot of a second arcuate component; a conjoined layer connected to a first surface of the first flange, the first surface configured to face a working fluid flow of the gas turbine; and a second flange shaped to be disposed within a second slot of the first arcuate component and a second adjacent slot of the second arcuate component, the second flange including a second surface connected to the conjoined layer.

A second aspect of the disclosure provides a gas turbine, including: a first arcuate component including a first slot and a second slot on an end of the first arcuate component; a second arcuate component located adjacent to the first arcuate component and including a first adjacent slot and a second adjacent slot on an end of the first arcuate component, the first adjacent slot and the second adjacent slot aligned with the first slot and the second slot of the first arcuate component; and a seal device including: a first flange disposed within the first slot of the first arcuate component and the first adjacent slot of the second arcuate component; a conjoined layer connected to a first surface of the first flange, the conjoined layer facing a working fluid flow of the gas turbine; and a second flange disposed within the second slot of the first arcuate component and the second adjacent slot of the second arcuate component, the second flange including a second surface connected to the conjoined layer.

A third aspect of the disclosure provides a gas turbine, including: a first arcuate component including a first slot and a second slot on an end of the first arcuate component, wherein an inner surface of the first arcuate component is exposed to a working fluid flow and an outer surface of the first arcuate component is exposed to a coolant flow; a second arcuate component located adjacent to the first arcuate component and including a first adjacent slot and a second adjacent slot on an end of the first arcuate component, the first adjacent slot and the second adjacent slot aligned with the first slot and the second slot of the first arcuate component, wherein the second arcuate component includes an adjacent outer surface and an adjacent inner surface, the adjacent inner surface exposed to the working fluid flow and the adjacent outer surface exposed to the coolant flow; and a first flange disposed within the first slot of the first arcuate component and the first adjacent slot of the second arcuate component; a conjoined layer connected to the first flange and facing the working fluid flow of the gas turbine; and a second flange connected to the conjoined layer and disposed within the second slot of the first arcuate component and the second adjacent slot of the second arcuate component.

These and other aspects, advantages and salient features of the invention will become apparent from the following detailed description, which, when taken in conjunction with the annexed drawings, where like parts are designated by like reference characters throughout the drawings, disclose embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of the invention will be better understood by reading the following more particular description of the invention in conjunction with the accompanying drawings.

FIG. 1 shows a perspective partial cut-away view of a known gas turbine.

FIG. 2 shows a perspective view of known arcuate components in an annular arrangement.

FIG. 3 shows a cross-sectional longitudinal view of a known turbine of a gas turbine.

FIG. 4 shows a cross-sectional end view of an arcuate component including a seal device disposed in connected slots in accordance with embodiments of the invention.

FIG. 5 shows a cross-sectional end view of an arcuate component including a seal device disposed in connected slots in accordance with embodiments of the invention.

FIG. 6 shows a cross sectional axial view along line A-A in FIG. 5 of one embodiment of two adjacent arcuate components with a seal device disposed in the slots in accordance with embodiments of the invention.

FIG. 7 shows a schematic view of portions of a multi-shaft combined cycle power plant in accordance with an aspect of the invention.

FIG. 8 shows a schematic view of portions of a single-shaft combined cycle power plant in accordance with an aspect of the invention.

It is noted that the drawings of the disclosure may not necessarily be to scale. The drawings are intended to depict only typical aspects of the disclosure, and therefore should not be considered as limiting the scope of the disclosure. It is understood that elements similarly numbered between the FIGURES may be substantially similar as described with reference to one another. Further, in embodiments shown and described with reference to FIGS. 1-8, like numbering may represent like elements. Redundant explanation of these elements has been omitted for clarity. Finally, it is understood that the components of FIGS. 1-8 and their accompanying descriptions may be applied to any embodiment described herein.

DETAILED DESCRIPTION OF THE INVENTION

As indicated herein, aspects of the invention provide for systems and devices shaped to reduce interface leakage through gaps between adjacent arcuate components in a gas turbine. These systems and devices include a unitary seal device (e.g., a conjoined seal device) which includes a first flange shaped to connect to/be disposed within a first slot of a first arcuate component and a first adjacent slot of a second arcuate component, and second flange shaped to connect to/be disposed within a second slot of the first arcuate component and a second adjacent slot of the second arcuate component. The first flange and the second flange are connected by a conjoined layer which forms a continuous surface across both the first flange and the second flange. The conjoined layer is integrated with/in to the first and second flanges and extends across a gap between the first arcuate component and the second arcuate component. The conjoined layer is located proximate a low pressure or hot gas path side of the seal and closes the gap between the first and second arcuate components, thereby forming a low pressure surface for both the first flange and the second flange on the hot gas path side. During operation of the gas turbine, the seal device/conjoined layer is forced toward (e.g., pressure loaded) the hot gas path of the gas turbine by a high pressure secondary cooling flow and sealingly engages/connects with portions of the first slot and the second slot. In contrast to conventional systems, which may include a third seal formed on top of adjacent planar seals disposed in the first and second arcuate components, embodiments of the current invention provide for a conjoined layer which is integral to both first and second flanges and is located on a low pressure side of the unitary seal device. The conjoined layer forms a continuous seal surface across/for the first and second flanges which spans the gap between the first and second arcuate components.

As used herein, the terms “axial” and/or “axially” refer to the relative position/direction of objects along axis A, which is substantially perpendicular to the axis of rotation of the turbomachine (in particular, the rotor section). As further used herein, the terms “radial” and/or “radially” refer to the relative position/direction of objects along axis (r), which is substantially perpendicular with axis A and intersects axis A at only one location. Additionally, the terms “circumferential” and/or “circumferentially” refer to the relative position/direction of objects along a circumference which surrounds axis A but does not intersect the axis A at any location.

Referring to FIG. 1, a perspective view of one embodiment of a gas turbine 2 is shown. In this embodiment, gas turbine 2 includes a compressor inlet 4, a compressor 6, a plurality of combustors 8, a compressor discharge 10, a turbine section 12 including a plurality of turbine blades 14, a rotor 16 and a gas outflow 18. Compressor inlet 4 supplies air to compressor 6. Compressor 6 supplies compressed air to combustors 8 where it mixes with fuel. Combustion gases from combustors 8 propels turbine blades 14 which rotate rotor 16 (generating power). A casing 20 forms an outer enclosure that encloses compressor inlet 4, compressor 6, plurality of combustors 8, compressor discharge 10, turbine section 12, turbine blades 14, rotor 16 and gas outflow 18. Gas turbine 2 is only illustrative; teachings of the invention may be applied to a variety of gas turbines.

Referring to FIG. 2, a perspective view of one embodiment of an annular arrangement 22 of arcuate components 24 of turbine section 12 of gas turbine 2 is shown. This view shows seven arcuate components 24 with one arcuate component removed for illustrative purposes. The end of each arcuate component 24 includes slots 26. Between each arcuate component 22 is a gap 28. A person skilled in the art will readily recognize that annular arrangement 22 may have any number of arcuate components 24; that arcuate components 24 may be of varying shapes and sizes; and that arcuate components 24 may serve different functions in gas turbine 2. For example, arcuate components in a turbine may include, but are not limited to, outer shrouds, inner shrouds, nozzle blocks, and diaphragms as discussed below.

Referring to FIG. 3, a cross-sectional view of one embodiment of turbine section 12 of gas turbine 2 (FIG. 1) is shown. In this embodiment, casing 20 encloses a plurality of outer shrouds 30, an inner shroud 32, a plurality of nozzle blocks 34, a plurality of diaphragms 36, and turbine blades 14. Each of the outer shrouds 30, inner shroud 32, nozzle blocks 34 and diaphragms 36 are arcuate components 24. Each of the outer shrouds 30, inner shrouds 32, nozzle blocks 34 and diaphragms 36 have slots 26 in a side thereof. In this embodiment, outer shrouds 30 connect to casing 20; inner shroud 32 connects to outer shrouds 30; nozzle blocks 34 connect to outer shrouds 30; and diaphragms 28 connect to nozzle blocks 34. A person skilled in the art will readily recognize that many different arrangements and geometries of arcuate components are possible. Alternative embodiments may include different arcuate components, more arcuate components, or less arcuate components.

Turning to FIG. 4, an end view of a first arcuate component 110 including a conjoined seal device 130 disposed in a first slot 120 and a second slot 122 on an end of first arcuate component 110 is shown according to embodiments of the invention. First slot 120 and second slot 122 connect to one another and are oriented at an angle ‘α’ relative to one another. Conjoined seal device 130 may include a first flange 132 (e.g., a shim) shaped to be disposed in first slot 120 and a second flange 134 (e.g., a shim) shaped to be disposed in second slot 122. First flange 132 and second flange 134 may be connected by a conjoined layer 136 which may contact first component surfaces 128 of first arcuate component 110. In an embodiment, conjoined seal device 130 and/or conjoined layer 136 may be pressed against first component surfaces 128 by a pressurized coolant flow 150 which has a pressure value which is higher than a pressure in a working fluid passage of turbine 2 (shown in FIG. 1). Conjoined layer 136 may span a gap 138 between first flange 132 and second flange 134 and form a substantially continuous surface across first flange 132 and second flange 134. In one embodiment, conjoined seal device 130 may include a laminate seal where conjoined layer 136 includes an outermost layer of the laminate seal. In another embodiment, first flange 132, second flange 134, and conjoined layer 136 may be formed as a unitary body. Conjoined layer 136 may include a first portion 170 connected to first flange 132 and a second portion 172 connected to second flange 134.

In an embodiment, a set of high pressure surfaces 127 (e.g., surfaces oriented to face a high pressure fluid flow, surfaces oriented to face secondary coolant flow, etc.) on first flange 132 and second flange 134 may be oriented at any angle ‘α’ relative to one another. In one embodiment, first portion 170 and second portion 172 of conjoined layer 136 may be oriented at any angle ‘ω’ relative to one another. In an embodiment, angle α may be less than about 90 degrees and angle ω may be greater than about 180 degrees.

As shown in FIG. 5, first flange 132 and second flange 134 may be oriented at any angle ‘α’ relative to one another and be connected by conjoined layer 136 in accordance with embodiments of the invention. In an embodiment, first flange 132 and second flange 134 may have a length of about 0.2 inches to about 24 inches. During operation, conjoined seal device 130 may contact first component surfaces 128 (shown in FIG. 4) forming a pressure boundary 180 (shown in phantom) between pressurized secondary coolant flows 150 and a working fluid flow 154 in the main gas path flow of turbine 2. Pressure boundary 180 may be formed between first arcuate component 110 and conjoined seal device 130 and may extend across an entirety of conjoined seal device 130. In an embodiment, a single continuous pressure boundary may be formed between conjoined layer 136 and first component surfaces 128 (e.g., locating contact between conjoined seal device 130 and first arcuate component 110 at pressure boundary 180). In an embodiment, conjoined seal device 130 may include a plurality of apertures/slots/features/tunnels configured to circulate a coolant flow through conjoined seal device 130.

Turning to FIG. 6, a cross sectional axial view along line A-A of FIG. 5 of first arcuate component 110 adjacent to a second arcuate component 210 is shown in accordance with embodiments of the invention. In an embodiment, gap 28 (e.g., an interface) is formed between first arcuate component 110 and second arcuate component 210 as a part of a thermal clearance. A first adjacent slot 222 and a second adjacent slot 220 (shown in phantom) on second arcuate component 210 are aligned with first slot 120 (shown in phantom) and second slot 122 such that conjoined seal device 130 may be disposed within first slot 120, second slot 122, first adjacent slot 220, and second adjacent slot 222 simultaneously. The disposition of first flange 132 and second flange 134 leaves a gap 138 (shown in phantom) between first flange 132 and second flange 134 which is spanned by conjoined layer 136 thereby forming a continuous surface as shown in FIG. 6. Gap 138 may be substantially defined by a bottom of first flange 132, a bottom of second flange 134 and conjoined layer 136. The continuous surface of conjoined layer 136 sealingly contacts inner surfaces 128 of slots 120, 122, 220, and 222, preventing leakage flow directly through gap 28 and/or slots 120, 122, 220, and 222. FIG. 6 shows first flange 132 disposed in first slot 120 and first adjacent slot 220; and second flange 134 disposed in second slot 122 and second adjacent slot 222. As can be seen in FIG. 6, conjoined layer 136 spans gap 28 and connects first flange 132 and second flange 134 across a substantially radially inward surface 128 of arcuate components 110 and 210.

In one embodiment, conjoined layer 136, first flange 132 and second flange 134 are integral to one another (e.g., formed as a substantially uniform body) and include at least one of laminate, silicate, ceramic, metal, a cloth-layer, a cloth-layer assemblage, and/or a foil-layer assemblage. For example metal, may include stainless steel and/or Inconel® from Huntington Alloys Corporation. A cloth layer comprises (and preferably consists essentially of) metal, ceramic, and/or polymer fibers which have been woven, knitted or pressed into a layer of fabric. The choice of layer construction (i.e. woven, knitted or pressed), the choice of materials for the cloth, and the choice of the thickness for a layer are made to meet the wear resistance, flexibility, and sealing requirements of a particular seal or connector application. In an embodiment, conjoined sealing device 130 may include intermittent layers of any materials now known or later developed. A person skilled in the art will readily recognize that conjoined layer 136, first flange 132 and second flange 134 may be composed of many materials.

Gas turbine 2 is only illustrative; teachings of the invention may be applied to any machine that disposes two or more seal components leaving a gap.

Turning to FIG. 7, a schematic view of portions of a multi-shaft combined-cycle power plant 900 is shown. Combined-cycle power plant 900 may include, for example, a gas turbine 980 operably connected to a generator 970. Generator 970 and gas turbine 980 may be mechanically coupled by a shaft 915, which may transfer energy between a gas turbine 980 and generator 970. Also shown in FIG. 7 is a heat exchanger 986 operably connected to gas turbine 980 and a steam turbine 992. Heat exchanger 986 may be fluidly connected to both gas turbine 980 and steam turbine 992 via conventional conduits (numbering omitted). Heat exchanger 986 may be a conventional heat recovery steam generator (HRSG), such as those used in conventional combined-cycle power systems. As is known in the art of power generation, HRSG 986 may use hot exhaust from gas turbine 980, combined with a water supply, to create steam which is fed to steam turbine 992. Steam turbine 992 may optionally be coupled to a second generator system 970 (via a second shaft 915). Any of generator system 970, gas turbine 980, HRSG 986, and steam turbine 992 may be connected to conjoined seal device 130 of FIG. 4 or other embodiments described herein. It is understood that generators 970 and shafts 915 may be of any size or type known in the art and may differ depending upon their application or the system to which they are connected. Common numbering of the generators and shafts is for clarity and does not necessarily suggest these generators or shafts are identical. Generator system 970 and second shaft 915 may operate substantially similarly to generator system 970 and shaft 915 described above. In one embodiment of the present invention (shown in phantom), purge flow control system 107 may be used, via computing device 110 to operate either or both of steam turbine 992 and gas turbine 980. In another embodiment, shown in FIG. 8, a single-shaft combined-cycle power plant 990 may include a single generator 970 coupled to both gas turbine 980 and steam turbine 992 via a single shaft 915. Gas turbine 980 and steam turbine 992 may be operably connected to conjoined seal device 130 of FIG. 4 or other embodiments described herein.

The conjoined laminate seal device of the present disclosure is not limited to any one power generation system, combined cycle power generation system, turbine or other system, and may be used with other power systems. Additionally, the device of the present invention may be used with other systems not described herein that may benefit from the sealing and leakage reduction provided by the conjoined laminate seal device described herein. While various embodiments are described herein, it will be appreciated from the specification that various combinations of elements, variations or improvements therein may be made by those skilled in the art, and are within the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. 

What is claimed is:
 1. A seal device, the seal device comprising: a first flange shaped to be disposed within a first slot of a first arcuate component and a first adjacent slot of a second arcuate component; a conjoined layer connected to a first surface of the first flange, the first surface configured to face a working fluid flow; and at least one secondary flange shaped to be disposed within a second slot of the first arcuate component and a second adjacent slot of the second arcuate component, the at least one secondary flange including a second surface connected to the conjoined layer.
 2. The seal device of claim 1, wherein the first flange and the at least one secondary flange include a plurality of layers.
 3. The seal device of claim 1, wherein the conjoined layer is integrated in to the first flange and the at least one secondary flange.
 4. The seal device of claim 1, wherein the conjoined layer is shaped to continuously contact the first slot and the second slot.
 5. The seal device of claim 1, wherein the conjoined layer includes a first portion connected to the first flange and a second portion connected to the at least one secondary flange, and wherein the first portion and the second portion are connected across a gap between the first flange and the at least one secondary flange and are shaped to form a continuous surface across both the first flange and the at least one secondary flange.
 6. The seal device of claim 1, wherein the at least one secondary flange is oriented at an angle relative to the first flange.
 7. The seal device of claim 1, wherein the conjoined layer is substantially the same width as the first flange and the at least one second flange, and wherein the conjoined layer forms the first surface of the first flange and the second surface of the at least one secondary flange.
 8. A gas turbine, comprising: a first arcuate component including a first slot and a second slot on an end of the first arcuate component; a second arcuate component located adjacent to the first arcuate component and including a first adjacent slot and a second adjacent slot on an end of the first arcuate component, the first adjacent slot and the second adjacent slot aligned with the first slot and the second slot of the first arcuate component; and a seal device including: a first flange disposed within the first slot of the first arcuate component and the first adjacent slot of the second arcuate component; a conjoined layer connected to a first surface of the first flange, the conjoined layer facing a working fluid flow of the gas turbine; and a second flange disposed within the second slot of the first arcuate component and the second adjacent slot of the second arcuate component, the second flange including a second surface connected to the conjoined layer.
 9. The gas turbine of claim 8, wherein the first flange and the second flange include a plurality of layers.
 10. The gas turbine of claim 8, wherein the conjoined layer is integrated in to the first flange and the second flange.
 11. The gas turbine of claim 8, wherein the conjoined layer is shaped to continuously contact the first slot and the second slot.
 12. The gas turbine of claim 8, wherein the conjoined layer includes a first portion connected to the first flange and a second portion connected to the second flange, and wherein the first portion and the second portion are connected across a gap between the first flange and the second flange and are shaped to form a continuous surface across both the first flange and the second flange.
 13. The gas turbine of claim 8, wherein the second flange is oriented at an angle relative to the first flange.
 14. The gas turbine of claim 8, wherein the conjoined layer is substantially the same width as the first flange and the second flange, and wherein the conjoined layer forms the first surface of the first flange and the second surface of the second flange.
 15. A gas turbine, comprising: a first arcuate component including a first slot and a second slot on an end of the first arcuate component, wherein an inner surface of the first arcuate component is exposed to a working fluid flow and an outer surface of the first arcuate component is exposed to a coolant flow; a second arcuate component located adjacent to the first arcuate component and including a first adjacent slot and a second adjacent slot on an end of the first arcuate component, the first adjacent slot and the second adjacent slot aligned with the first slot and the second slot of the first arcuate component, wherein the second arcuate component includes an adjacent outer surface and an adjacent inner surface, the adjacent inner surface exposed to the working fluid flow and the adjacent outer surface exposed to the coolant flow; and a first flange disposed within the first slot of the first arcuate component and the first adjacent slot of the second arcuate component; a conjoined layer connected to the first flange and facing the working fluid flow of the gas turbine; and a second flange connected to the conjoined layer and disposed within the second slot of the first arcuate component and the second adjacent slot of the second arcuate component.
 16. The gas turbine of claim 15, wherein the conjoined layer is integrated in to the first flange and the second flange.
 17. The gas turbine of claim 15, wherein the conjoined layer is shaped to continuously contact the first slot and the second slot.
 18. The gas turbine of claim 15, wherein the second flange is oriented at an angle relative to the first flange.
 19. The gas turbine of claim 15, wherein conjoined layer includes a first portion connected to the first flange and a second portion connected to the second flange, and wherein the first portion and the second portion are connected across a gap between the first flange and the second flange and are shaped to form a continuous surface across both the first flange and the second flange.
 20. The gas turbine of claim 15, wherein the conjoined layer is substantially the same width as the first flange and the second flange, and wherein the conjoined layer forms the first surface of the first flange and the second surface of the second flange. 